Medical Assistant Exam: The Basics of Anatomy and Physiology

Anatomy is the study of the structures of the body, while physiology is the study of the functions of the body and its structures.

Structural Units of the Human Body
The human body is a complex organism composed of various levels of structure. The levels of structure include cells, tissues, organs, system, and organism. Each structure has a specific function that aids in the overall function of the human body.

Cells
Cells are the structural and functional units of the human body. The study of cells is called cytology. Homeostasis, or the tendency of the body toward a state of equilibrium, depends on the interaction between the cell and its environment. During development, cells become specialized in size, shape, characteristics, and function, resulting in a large variety of types of cells in the body.
Every cell in the body is enclosed by a plasma cell membrane. The plasma membrane separates the material outside of the cell (extracellular) from the material inside the cell (intracellular). It maintains the integrity of the cell; if the plasma cell membrane ruptures or is broken, the cell dies. The plasma cell membrane determines what can go into or out of the cell. The main structural components of the plasma cell membrane are phospholipids and proteins.
The cytoplasm is the gel-like fluid inside the cell. The cytoplasm has numerous small structures, called organelles, suspended in it. These organelles are the functional machinery of the cell, and each organelle type has a specific role in the metabolic reactions that take place in the cytoplasm.
The cytoplasm consists primarily of liquid known as the intracellular fluid. Intracellular fluid is made up of a complex mix of substances dissolved in water. About two-thirds of the water in the body is in the cytoplasm of cells. The intracellular fluid contains dissolved electrolytes, metabolic waste products, and nutrients such as amino acids and simple sugars.
The nucleus is the control center that directs the activities of the cell. All cells have at least one nucleus at some time during their existence; some, however, such as red blood cells, lose their nucleus as they mature. Other cells, such as skeletal muscle cells, have multiple nuclei.
The nucleus is a relatively large, spherical body that is usually located near the center of the cell. It is enclosed by a double-layered nuclear membrane that separates the cytoplasm of the cell from the nucleoplasm, the fluid portion inside the nucleus.
The nucleus contains the genetic material of the cell. In the nondividing cell, the genetic material deoxyribonucleic acid (DNA), is present as long, slender, filamentous threads called chromatin. When the cell starts to divide or replicate, the chromatin condenses and becomes tightly coiled to form short, rodlike chromosomes.

Tissues
Tissues are groups of cells that are similar in structure and function. The study of tissues is called histology. The four major types of tissues of the body are epithelial, connective, muscle, and nervous.

Epithelial Tissue
Epithelial tissue covers organ surfaces; lines cavities, vessels, and canals; and provides the secreting portions of glands. Its function is to protect, absorb, secrete, and filtrate.

Connective Tissue
Connective tissue includes bones, cartilage, blood cells, and fat cells. Its function is to protect, support, and connect other tissues and organs.

Muscle Tissue
Muscle tissue contracts to produce movement. The three types of muscle tissue are skeletal, cardiac, and smooth. Skeletal muscle is attached to bones and causes voluntary movement of body parts. Cardiac muscle is located only in the heart and causes involuntary heart contractions. Smooth muscle also involves involuntary contractions, but within the walls of hollow organs and blood vessels.

Nervous Tissue
Nervous tissue consists of neurons that receive and conduct electrochemical impulses.

Organs
Organs are body structures that consist of several tissues and perform specialized functions. Organs include structures such as the brain, stomach, skin, nose, nasopharynx, bladder, heart, liver, lungs, spleen, thymus, thyroid, kidney, uterus, intestines, gall bladder, ovaries, prostate, and testes.

Systems
A system is an organized grouping of structure, including the integumentary system, musculoskeletal system, cardiovascular system, respiratory system, digestive system, urinary system, reproductive system, endocrine system, sensory system, and the nervous system.
- The integumentary system includes the skin and its appendages, hair, nails, and glands. This system protects the body from potentially harmful external elements and helps to regulate the body’s temperature, among other functions.
- The musculoskeletal system is comprised of muscles, tendons, and associated structures. This system makes movement possible, moves body fluid, and generates body heat.
- The cardiovascular system consists of the heart, arteries, veins, capillaries, and blood. This system circulates blood throughout the body to transport oxygen and nutrients to cells and to carry waste products to the kidneys, where waste is removed by filtration.
- The respiratory system consists of the nose, pharynx, trachea, larynx, and lungs. This system brings oxygen into the body for transportation to the cells. It also removes carbon dioxide and some water waste from the body.
- The urinary system consists of the kidneys, ureters, urinary bladder, and urethra. This system filters blood to remove waste and maintains the electrolyte and fluid balance within the body.
- The male reproductive system consists of the penis and testicles. The female reproductive system consists of the ovaries, uterus, and vagina. The reproductive system produces new life.
- The endocrine system consists of the adrenal glands, gonads, pancreas, parathyroids, pineal, pituitary, thymus, and thyroid. This system is responsible for integrating all body functions.
- The digestive system consists of the mouth, esophagus, stomach, small intestine, large intestine, liver, and pancreas. This system is responsible for the digestion of food, so that nutrients from the food can be absorbed into the bloodstream and waste can be eliminated.
- The sensory system consists of the organs of sight, hearing, smell, taste, and touch. This system is responsible for sight, hearing, taste, and sensations.
- The nervous system consists of the nerves, brain, and spinal cord. This system is responsible for coordinating the reception of stimuli.

Anatomical Divisions
Observing the relative locations and organization of internal body parts requires sectioning the body along various regions.
- hypochondriac region: upper lateral regions beneath the ribs
- epigastric region: middle lateral regions
- umbilical region: region of the navel
- inguinal regions: lower lateral groin regions
- hypogastric region: region below the navel

Positions and Directions
Directional terms are used to describe the relative position of one part of the body to another.
- Superior means that one part is above another part or closer to the head. The nose is superior to the mouth.
- Inferior means that one part is below another part or closer to the feet. The heart is inferior to the neck.
- Anterior means toward the front surface. The heart is anterior to the vertebral column.
- Posterior means toward the back. The heart is posterior to the sternum.
- Medial means toward or nearer the midline of the body. The nose is medial to the ears.
- Lateral means toward or nearer the side, away from the midline. The ears are lateral to the eyes.
- Proximal means that one part is closer to a point of attachment, or closer to the trunk of the body, than another part. The elbow is proximal to the wrist.
- Distal means that one part is farther away from a point of attachment than another part is. The fingers are distal to the wrist.
- Superficial means located on or near the surface. The superficial layer of the skin is the epidermis.
- Deep means away from the surface. Muscles are deep to the skin surface.
- Visceral pertains to internal organs or the covering of the organs. The visceral pericardium covers the heart.
- Parietal refers to the wall of a body cavity. The parietal peritoneum lines the wall of the abdominal cavity.

Body Planes
To aid in visualizing the spatial relationships of internal body parts, anatomists use three imaginary planes, each of which cuts through the body in a different direction.

1. Sagittal plane refers to a lengthwise cut that divides the body into right and left portions; sometimes called a longitudinal section.
Midsagittal, or median, plane refers to a cut that passes through the midline of the body that divides the body into equal right and left halves.

2. Transverse plane, or horizontal plane, is perpendicular to the sagittal plane and cuts across the body horizontally to divide it into superior and inferior portions. Sections cut this way are sometimes called cross sections.

3. Frontal plane divides the body into anterior and posterior portions. It is perpendicular to both the sagittal plane and the transverse plane; sometimes called a coronal plane.

Common Diseases and Pathology of Each Body System
Pathology is the study and diagnosis of disease through examination of organs, tissues, bodily fluids, and whole bodies (autopsies). Anything that upsets the normal structure or working of the body is considered a disease and is studied as the science of pathology.

Integumentary System
The integumentary system consists of the skin and its accessory organs. The skin, which is the largest organ in the body, is composed of three layers, the epidermis, dermis, and subcutaneous. The accessory organs include the glands, hair, and nails.
The functions of the skin and its accessory organs include:
- Protection: The skin protects the body from sunlight, microorganisms, and other harmful elements. In addition, hair in the nasal and ear cavities, as well as on the eyelids, helps protect against harmful microorganisms by trapping them and not allowing them to enter the body. Nails help protect the ends of the fingers and toes.
- Secretion: Sebaceous glands secrete sebum to help lubricate the skin, while sudoriferous glands secrete sweat to help cool the body when the environment is too hot.
- Sensation: The skin contains sensory touch receptors that allow the person to feel temperature, pain, and touch.
- Temperature regulation: The skin plays an important role in insulating the body and maintaining heat when the body is exposed to cold temperatures. The production of sweat by the sudoriferous glands aids in cooling off the body when the environment is too hot.

Related Conditions and Diseases
- psoriasis: a chronic inflammatory skin disease characterized by red or pink patches covered by thick, dry, silvery scales
- urticaria: an inflammatory skin eruption, usually caused by an allergic reaction, which is characterized by red patches called wheals; also known as hives
- alopecia: a partial or complete loss of hair, especially on the head
- dermatitis: an inflammation of the skin characterized by severe itching, redness, and the appearance of small skin vesicles
- pediculosis: an infestation of lice characterized by severe itching; commonly transmitted through the use of brushes, combs, or hats that have been used by an infected person
- decubitis ulcers: commonly known as bedsores or pressure sores; localized open sores, frequently seen over a bony prominence, due to persistent pressure and poor blood flow to the area
- scabies: a contagious infestation of the skin caused by the itch mite; characterized by severe itching and lesions
- warts: benign, circumscribed, raised lesions due to hypertrophy, or exaggerated growth, of the papillae and epidermis; commonly caused by the papilloma virus
- shingles: a painful, inflammatory skin condition characterized by the eruption of vesicles, or raised blisterlike protuberances; caused by the herpes zoster virus
- skin cancer: a cancer that is caused by overexposure to the ultraviolet rays of the sun as well as exposure to radiation. There are three forms: basal cell carcinoma, squamous cell carcinoma, and malignant melanoma.
- hematoma: the accumulation of blood under the skin due to a break in a blood vessel; also known as a bruise
- impetigo: an infectious skin infection caused by staphyloccocal and/or streptococal bacteria
- schleroderma: a chronic autoimmune disease characterized by hardening of the skin, which becomes taunt, firm, and edematous, or swollen

Musculoskeletal System
The musculoskeletal system consists of bones, cartilage, joints, muscles, ligaments, and tendons. Its function is to provide support and protection for the body’s structures, as well as to allow for physical movement.

Related Conditions and Diseases
- kyphosis: abnormal outward curvature of the spine
- scoliosis: abnormal sideward curvature of the spine
- lordosis: abnormal inward curvature of the spine
- osteoporosis: metabolic bone disease characterized by decreased bone mass
- osteomyelitis: infection of the bone-forming tissue, characterized by inflammation and swelling over the affected bone
- fracture: a break in the bone characterized by swelling, pain, and tenderness at and around the site of the injury, possible deformity, and limited range of motion
- rheumatoid arthritis: a chronic connective tissue disease characterized by painful and swollen joints that may result in deformities and immobility
- gout: a form of arthritis characterized by the accumulation of uric acid crystals in various joints
- bursitis: inflammation of the bursa commonly affecting areas such as the shoulder, arm, and elbow
- tendonitis: inflammation of the tendon commonly affecting the shoulder rotator cuff, hip, or hamstring
- sprain: an injury to a ligament that causes pain and limited range of motion
- myasthenia gravis: a chronic autoimmune neuromuscular disease characterized by muscle weakness and abnormal fatigue
- carpal tunnel syndrome: compression of the median nerve in the hand and wrist that is characterized by pain, tingling, and numbness; usually seen in patients who perform repetitive motion tasks or jobs
- muscular dystrophy: a progressive congenital disorder characterized by the wasting of skeletal muscle tissue

The Nervous System
The nervous system controls the body’s response to stimuli and helps maintain homeostasis. It helps control both voluntary and involuntary functions. The nervous system has two major parts:
- The central nervous system, which consists of the brain and spinal cord. The function of the central nervous system is to receive and process information and to regulate all bodily activity.
- The peripheral nervous system, which consists of 31 pairs of spinal nerves and 12 cranial nerves. The function of the peripheral nervous system is to transmit nerve signals to and from the central nervous system.

Related Conditions and Diseases
- migraine headaches: severe, pulsating headaches that are usually accompanied by vision and gastrointestinal disturbances
- concussion: a trauma or blow to the head causing the brain to strike the skull; may cause confusion and temporary unconsciousness
- hemiplegia: a spinal cord injury in which there is paralysis on one side of the body
- paraplegia: a spinal cord injury in which there is paralysis of the lower half of the body (trunk and legs)
- quadriplegia: a spinal cord injury in which there is paralysis of all four extremities and usually the trunk of the body
- cerebrovascular accident: a vascular injury to the brain characterized by a sudden loss of neurological function; also known as a stroke
- transient ischemic attack: a brief disruption of blood flow to the brain, causing temporary impairment of neurological function
- epilepsy: abnormal electrical discharges within the brain causing recurrent seizures, sensory disturbances, abnormal behavior, and/or loss of consciousness
- meningitis: inflammation of the meninges and cerebral spinal fluid commonly caused by an infectious agent such as bacteria or viruses
- encephalitis: inflammation of the brain commonly caused by an infectious agent such as bacteria or viruses
- Bell’s palsy: a condition of temporary weakness or paralysis of one side of the face
- Alzheimer’s disease: a form of pre-senile dementia, characterized by memory loss, deterioration of intellectual function, disorientation, and emotional instability
- Parkinson’s disease: a chronic progressive disease of the central nervous system characterized by movement disorders and changes in mood and cognition
- multiple sclerosis: a chronic disease of the central nervous system characterized by the degeneration of the myelin sheath that covers nerve fibers

The Cardiovascular, Hematopoietic, and Lymphatic Systems
The cardiovascular system consists of the heart and related blood vessels (arteries, veins, and capillaries), also known as the circulatory system. The function of the cardiovascular system is to pump and distribute blood throughout the body and deliver oxygen and other nutrients to every organ, tissue, and cell of the body.
The hematopoietic system consists of the blood cells produced by the bone marrow. These cells consist of the erythrocytes, leukocytes, and thrombocytes. In the hematopoietic system, each of the blood cells has its distinct function. The erythrocyte is responsible for transporting oxygen throughout the body and for transporting carbon dioxide to the lungs to be expelled by the body. Leukocytes are responsible for fighting off infection and for producing antibodies. Thrombocytes are responsible for blood clotting and play a role in the coagulation process.

The lymphatic system consists of the tissue fluid called lymph, lymph vessels, and lymph nodes. Organs related to the lymph system include the thymus gland and spleen. The lymphatic system has three primary functions:
- to transport immune cells to and from the lymph nodes
- to remove interstitial fluid from tissues
- to filter harmful substances such as viruses and bacteria from the lymph nodes

Related Conditions and Diseases
- myocardial infarction: occlusion of blood flow within a coronary artery, which in turn causes damage to the heart muscle; also known as a heart attack
- coronary artery disease: a narrowing or blockage of any of the coronary arteries that supply blood to the heart
- congestive heart failure: inability of the heart to pump efficiently, causing fluid to build up the lungs or peripheral body areas
- angina pectoris: chest pain or pressure around the heart caused by a deficiency of oxygen supply to the heart muscle
- endocarditis: inflammation of the endocardium, the membrane lining the heart cavities, and the heart valves
- hypertension: high blood pressure
- aneurysm: weakness in an artery wall that causes the artery to bulge and/or rupture
- arteriosclerosis: thickening of an artery wall
- atherosclerosis: the accumulation of cholesterol in the artery wall
- thrombophlebitis: inflammation of a vein combined with clot formation
- iron deficiency anemia: a decrease in the number of red blood cells resulting from a decrease in iron
- aplastic anemia: decreased production of red blood cells by the bone marrow
- sickle cell anemia: anemia due to an abnormal red blood cell morphology and function, in which the cells are shaped like a sickle
- lymphedema: abnormal accumulation of fluid due to obstruction of lymph vessels
- Hodgkin’s lymphoma: a type of cancer affecting the lymph nodes and eventually spreading throughout the lymphatic system to affect the spleen and bone marrow
- leukemia: malignancy of the blood and blood-forming tissues; characterized by the blood cell being affected and also classified as chronic or acute

The Respiratory System
The respiratory system consists of the upper respiratory tract and the lower respiratory tract. The function of the respiratory system is to facilitate breathing and to provide for gas exchange to all parts of the body.
- The upper respiratory tract includes the nose and nasal cavities, pharynx, larynx, and upper trachea.
- The lower respiratory tract includes the lower trachea, bronchi, and lungs.

Related Conditions and Diseases
- epistaxis: nosebleed
- pneumonia: an inflammatory condition of the lungs commonly caused by infectious microorganisms
- bronchitis: inflammation of the bronchi of the lungs
- sinusitis: inflammation of the sinuses
- acute pharygitis: inflammation of the throat characterized by pain and redness, and commonly caused by streptococcal bacteria
- pneumothorax: air in the chest cavity
- hemothorax: blood in the chest cavity
- pleurisy: an inflammation of the lining of the lungs that causes pain during breathing or coughing
- emphysema: a chronic progressive disease of the lungs characterized by shortness of breath
- tuberculosis: an infection of the lungs caused by mycobacterium; characterized by chronic cough, blood-tinged sputum, weight loss, and night sweats
- croup: inflammation of the upper airways; characterized by a barking cough
- pulmonary embolism: a sudden blockage in a lung artery, usually caused by a blood clot

The Digestive System
The digestive system consists of the digestive tract and the accessory organs of digestion. The digestive tract contains structures such as the mouth, tongue, teeth, gums, uvula, and esophagus. Organs associated with the digestive tract include the stomach, small intestine, large intestine, rectum, and anus. The accessory organs include the gall bladder, liver, and pancreas.
The functions of the digestive system include the breakdown of food, digestion of nutrients, and elimination of wastes.

Related Conditions and Diseases
- gastritis: inflammation of the stomach
- gastroesophageal reflux disease (GERD): a condition in which the liquid content of the stomach regurgitates (backs up or refluxes) into the esophagus; commonly referred to as acid reflux
- gastroenteritis: inflammation of the stomach and intestines
- hiatal hernia: a condition in which a portion of the stomach protrudes upward into the chest, through an opening in the diaphragm
- peptic ulcer: a hole in the lining of the stomach or duodenum characterized by abdominal pain and usually caused by the bacterium Helicobacter pylori
- celiac disease: an autoimmune disease in which the lining of the small intestine is damaged from eating gluten and other proteins found in wheat, barley, rye, and possibly oats
- irritable bowel syndrome: a disorder of the lower intestinal tract characterized by abdominal pain, cramping, bloating, constipation, and diarrhea
- Crohn’s disease: a chronic inflammation of the digestive tract, characterized by abdominal cramping, fever, fatigue, and persistent watery diarrhea
- ulcerative colitis: inflammation and ulcers of the lining of the colon and rectum characterized by abdominal pain and bloody diarrhea
- acute appendicitis: inflammation of the appendix
- cholelithiasis: gallstones
- hepatitis: inflammation of the liver, usually caused by viruses
- pancreatitis: inflammation of the pancreas
- jaundice: yellowish coloring of the skin because of an increase of bilirubin in the bloodstream
- hemorrhoids: condition in which the veins around the anus or lower rectum are swollen and inflamed

The Urinary System
The urinary system consists of the kidneys, ureters, urinary bladder, and urethra. The functions of the urinary system are to filter the blood, regulate fluid and electrolytes, and excrete wastes.

Related Conditions and Diseases
- glomerulonephritis: inflammation of the glomeruli of the kidney
- polycystic disease: genetic disorder characterized by the growth of numerous cysts in the kidneys
- uremia: presence of urine in the bloodstream
- nephrotic syndrome: a syndrome caused by various disorders that damage the kidneys and characterized by protein in the urine
- renal calculi: painful condition of stones in the kidney, characterized by blood in the urine and severe pain radiating from the back, down the flank, and into the groin
- cystitis: inflammation of the bladder, usually caused by a bacterial infection
- urethritis: inflammation of the urethra
- neurogenic bladder: condition in which the bladder does not empty properly due to a neurological problem
- end-stage renal disease: irreversible kidney failure

The Reproductive System
The female reproductive system consists of the breasts, ovaries, fallopian tubes, uterus, cervix, and vagina. The function of the reproductive system is to bear offspring. The male reproductive system consists of the penis, urethra, testes, scrotum, and prostate gland. The function of the male reproductive system is the production and transportation of sperm for the purpose of reproduction.

Related Conditions and Diseases—Female Reproductive System
- premenstrual syndrome (PMS): a condition characterized by anxiety, mood swings, fatigue, depression, headaches, vertigo, bloating, acne, swollen breasts, and changes in appetite that typically occur seven to ten days prior to menstruation and end a few days after the onset of menstruation
- amenorrhea: absence of menstruation
- dysmenorrhea: pain during menstruation
- ovarian cysts: benign fluid-filled sacs that form on the ovary
- endometriosis: an abnormal condition of endometrial tissue occurring and growing outside the endometrium
- pelvic inflammatory disease (PID): a condition resulting from the extension of infections from the reproductive organs into the pelvic cavity; often involves the peritoneum
- menopause: the cessation of menstruation; usually occurs in women between the ages of 40–58
- cervical cancer: cancer of the cervix typically caused by the human papillomavirus (HPV)
- sexually transmitted diseases (STDs): diseases such as gonorrhea, chlamydia, herpes, syphilis, and AIDS that are caused by various infectious microorganisms and are contracted during sexual activity; affects both male and female reproductive systems

Related Conditions and Diseases—Male Reproductive System
- prostatitis: inflammation of the prostate
- epididymitis: inflammation of the epididymis
- orchitis: inflammation of the testes
- cryptorchism: condition of the testes in which the testes have not descended properly into the scrotum
- benign prostatic hyperplasia: a progressive condition characterized by enlargement of the prostate and obstruction of the urethra
- prostatic cancer: malignant tumor of the prostate gland
- testicular cancer: malignant tumor of a testis
- hydrocele: swelling of the testes
- impotence: inability to sustain an erection

The Endocrine System
The endocrine system is responsible for regulating the body’s metabolic activities through the secretion of hormones by various glands within the system. The endocrine glands include the hypothalamus, pineal gland, thryroid gland, parathyroid glands, thymus glands, pancreas, adrenal glands, ovaries, and testes.

Related Conditions and Diseases
- thyroiditis: inflammation of the thyroid gland
- hyperthyroidism: overactive thyroid gland characterized by the oversecretion of thyroid hormones; also known as Graves disease
- hypothyroidism: underactive thyroid gland characterized by the undersecretion of thyroid hormones; also known as myxedema
- hyperparathyroidism: excessive secretion of parathyroid hormone that affects phosphate and calcium metabolism
- hypoparathyroidism: undersecretion of parathyroid hormone resulting in hypocalcemia
- diabetes mellitus: a chronic disorder of carbohydrate metabolism resulting from inadequate amounts of insulin, characterized by increased glucose in the bloodstream and urine
- hypoglycemia: abnormal decrease in blood glucose levels characterized by acute fatigue, malaise, irritability, and weakness
- Cushing’s disease: hormone disorder caused by high levels of glucocorticoids secreted by the adrenal cortex
- Addison’s disease: decrease in production of steroid hormones by the adrenal glands
- hyperpituitarism: oversecretion of growth hormone by the pituitary gland

The Sensory System
The sensory system is responsible for vision, hearing, touch, taste, and smell. Organs within the system include the eyes, ears, nose, and tongue.

Related Conditions and Diseases
- myopia: nearsightedness
- hyperopia: farsightedness
- presbyopia: a form of farsightedness that occurs with age
- astigmatism: a defect in sight caused by changes in the curvature over certain portions of the cornea and lens of the eye
- conjunctivitis: inflammation of the conjunctiva, the membrane lining the inside of the eyelid; typically caused by a microorganism
- blepharitis: inflammation of the eyelids
- glaucoma: damage to the retina and optic nerve because of an increase in fluid pressure within the eye
- macular degenerative disease: a degenerative disease of the retina (a thin layer of nerve cells that lines the back of the eyeball) that causes progressive loss of central vision
- cataract: clouding of the eye lens, causing a decrease in visual acuity
- otitis media: inflammation of the inner ear
- otitis externa: inflammation of the external ear
- otosclerosis: abnormal condition causing the formation of spongy bone in the ear resulting in a progressive loss of hearing
- Meniere’s disease: progressive condition characterized by ringing in the ears, dizziness, and a sensation of pressure in the ears
- presbycusis: impairment of hearing that occurs with age
- deafness: complete or partial loss of hearing
- tinnitus: ringing in the ear
- vertigo: a disturbance in equilibrium characterized by the feeling of moving around in space